<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title>glDebugMessageCallback - OpenGL ES 3.2 Reference Pages</title>
    <link rel="stylesheet" type="text/css" href="opengl-man.css"/>
    <meta name="generator" content="DocBook XSL Stylesheets V1.78.1"/>
    <script type="text/x-mathjax-config">
            MathJax.Hub.Config({
                MathML: {
                    extensions: ["content-mathml.js"]
                },
                tex2jax: {
                    inlineMath: [['$','$'], ['\\(','\\)']]
                }
            });
        </script>
    <script type="text/javascript" src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML"/>
  </head>
  <body>
    <header/>
    <div class="refentry" id="glDebugMessageCallback">
      <div class="titlepage"/>
      <div class="refnamediv">
        <h2>Name</h2>
        <p>glDebugMessageCallback — specify a callback to receive debugging messages from the GL</p>
      </div>
      <div class="refsynopsisdiv">
        <h2>C Specification</h2>
        <div class="funcsynopsis">
          <table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
            <tr>
              <td>
                <code class="funcdef">void <strong class="fsfunc">glDebugMessageCallback</strong>(</code>
              </td>
              <td>DEBUGPROC <var class="pdparam">callback</var>, </td>
            </tr>
            <tr>
              <td> </td>
              <td>void * <var class="pdparam">userParam</var><code>)</code>;</td>
            </tr>
          </table>
          <div class="funcprototype-spacer"> </div>
        </div>
      </div>
      <div class="refsect1" id="parameters">
        <h2>Parameters</h2>
        <div class="variablelist">
          <dl class="variablelist">
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>callback</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    The address of a callback function that will be called when a debug message is generated.
                </p>
            </dd>
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>userParam</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    A user supplied pointer that will be passed on each invocation of <em class="parameter"><code>callback</code></em>.
                </p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1" id="description">
        <h2>Description</h2>
        <p>
            <code class="function">glDebugMessageCallback</code> sets the current debug output callback function to
            the function whose address is given in <em class="parameter"><code>callback</code></em>. The callback function
            should have the following prototype (in C), or be otherwise compatible with such a prototype:
        </p>
        <pre class="programlisting">        typedef void (APIENTRY *DEBUGPROC)(GLenum source,
            GLenum type,
            GLuint id,
            GLenum severity,
            GLsizei length,
            const GLchar *message,
            const void *userParam);</pre>
        <p>
            This function is defined to have the same calling convention as
            the GL API functions. In most cases this is defined as
            <code class="code">APIENTRY</code>, although it will vary depending on
            platform, language and compiler.
        </p>
        <p>
            Each time a debug message is generated the debug callback
            function will be invoked with <em class="parameter"><code>source</code></em>,
            <em class="parameter"><code>type</code></em>, <em class="parameter"><code>id</code></em>, and
            <em class="parameter"><code>severity</code></em> associated with the message, and
            <em class="parameter"><code>length</code></em> set to the length of debug message
            whose character string is in the array pointed to by
            <em class="parameter"><code>message</code></em> <em class="parameter"><code>userParam</code></em>
            will be set to the value passed in the
            <em class="parameter"><code>userParam</code></em> parameter to the most recent
            call to <code class="function">glDebugMessageCallback</code>.
        </p>
      </div>
      <div class="refsect1" id="notes">
        <h2>Notes</h2>
        <p>
            When the GL is in use remotely, the server may not be able to
            call functions in the client's address space. In such cases, the
            callback function may not be invoked and the user should
            retrieve debug messages from the context's debug message log by
            calling
            <a class="citerefentry" href="glGetDebugMessageLog.xhtml"><span class="citerefentry"><span class="refentrytitle">glGetDebugMessageLog</span></span></a>.
        </p>
      </div>
      <div class="refsect1" id="versions">
        <h2>Version Support</h2>
        <div class="informaltable">
          <table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
            <colgroup>
              <col style="text-align: left; "/>
              <col style="text-align: center; " class="firstvers"/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; " class="lastvers"/>
            </colgroup>
            <thead>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; ">
                 
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; " colspan="4">
                <span class="bold"><strong>OpenGL ES API Version</strong></span>
            </th>
              </tr>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>Function Name</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>2.0</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.0</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.1</strong></span>
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.2</strong></span>
            </th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; ">
                  <code class="function">glDebugMessageCallback</code>
                </td>
                <td style="text-align: center; border-right: 2px solid ; ">-</td>
                <td style="text-align: center; border-right: 2px solid ; ">-</td>
                <td style="text-align: center; border-right: 2px solid ; ">-</td>
                <td style="text-align: center; ">✔</td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <div class="refsect1" id="seealso">
        <h2>See Also</h2>
        <p>
            <a class="citerefentry" href="glDebugMessageControl.xhtml"><span class="citerefentry"><span class="refentrytitle">glDebugMessageControl</span></span></a>,
            <a class="citerefentry" href="glDebugMessageInsert.xhtml"><span class="citerefentry"><span class="refentrytitle">glDebugMessageInsert</span></span></a>,
            <a class="citerefentry" href="glGetDebugMessageLog.xhtml"><span class="citerefentry"><span class="refentrytitle">glGetDebugMessageLog</span></span></a>.
        </p>
      </div>
      <div class="refsect1" id="Copyright">
        <h2>Copyright</h2>
        <p>
            Copyright <span class="trademark"/>© 2013-2015 Khronos Group.
            This material may be distributed subject to the terms and conditions set forth in
            the Open Publication License, v 1.0, 8 June 1999.
            <a class="link" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
        </p>
      </div>
    </div>
    <footer/>
  </body>
</html>
